Welding is commonly employed as an assembly method for joining several metal parts or sheet materials together into an assembly. Various welding methods are available, such as arc and resistant spot welding.
Recently, laser welding has been developed and has provided several advantages over more conventional forms of welding. The sharp focusing of the laser beam allows a concentration of energy capable of providing faster welding with less heat being introduced into the surrounding portions of the parts. Laser welding is also an extremely precise and accurate process, and once the metal sheet materials are properly clamped, repeatability on a production basis becomes a concern. In mass production laser welding operations, the precision with which the laser beam must be focused frequently greatly exceeds the degree of precision possible in positioning the sheet metal parts to be welded. Variances created in manufacturing tolerances, clamping fixture tolerances, and the tolerances within the parts themselves can all introduce errors in positioning the metal sheets relative to the laser beam focusing head which are many times greater than the maximum permissible variation of position relative to the point at which the laser beam is focused. Even programmable robotic arms are programmed with reference to a fixed origin and, therefore, cannot compensate for the tolerances created in the system. Without some form of guidance to compensate for the tolerances built within the system, accurate and repeatable positioning of the welds cannot be obtained.
Attempts have been made to remedy the problem by fixedly mounting the laser welder through an aperture in the clamping region of the clamp. This ensures that the metal sheets are clamped together in continuous contact while also ensuring for the proper positioning of the laser welder. Unfortunately, after a certain amount of use, the aperture in the clamp may become clogged, thus prohibiting the laser welder from providing a high quality weld. The clogging of the aperture in the clamp creates inefficiencies in manufacturing that are undesirable on a production basis.
Although laser welding has many applications, it is particularly well suited for production line welding of sheet metal body panels of an automobile. Typically, the body panels are loosely assembled and transported to a welding station. At the welding station, a clamping system is imposed to hold the body panels while the welding operations are performed.
Due to the configuration of the body panels, certain clamping and welding apparatus cannot be utilized in certain areas of the body panels as space limitations may limit the amount of space available for the necessary maneuvering and the proper functioning of the clamping and welding apparatus. Therefore, in order to maximize productivity and efficiency, several different configurations of clamping and welding apparatus must be utilized within one welding station depending on the configuration, speed and cost of the clamping and welding apparatus.